As is well known, internal combustion explosion engines, particularly four-stroke engines, have the drawback of not achieving satisfactory volumetric efficiency at each engine r.p.m. because of various phenomena, mainly the low pressure in the intake duct, the low quantity of fresh gas pushed into the cylinder, and the presence of residual spent gas therein. As a consequence, an irregular power curve is generated, with non-optimum power regulation.
This problem, much felt by the expert, has been confronted by providing the engine with turbo-compressors, supplementary flap valves, variable timing diagrams, ducts of variable length, throttle controls which open and close one and then another intake duct, megaphone exhausts, exhausts with resonance chambers, supplementary electronically controlled exhaust valves, etc. The results, nearly always obtained by costly and technically complicated arrangements, in all cases leave considerable room for improvement. In this respect, technological progress has meant that very high maximum power levels are reached at high r.p.m., to the detriment of the power at low r.p.m. Moreover, and in particular, this power is delivered irregularly and with high specific fuel consumption.
In addition to the aforesaid it must be noted that the search for improved performance by the expert can lead to an exaggerated increase in the cross-sections of the intake and exhaust ducts, producing the opposite effect to that required. In this respect, by enlarging these ducts beyond a certain limit, the velocity of the gas column is reduced, with consequent throughput reduction.
German Patent Publication No. DE 1 914 859 describes a tubular body suitable to be located between the engine and the carburetor and containing within it an internal element which is substantially barrel shaped. At its end which is directed towards the engine, the element has a funnel-shaped cavity wherein a conical element is located. The conical element's apex is directed towards the engine. According to the prior art, the known solution affects the gas flow which is directed towards the engine and also the flow of the gas which, already undrawn by the engine, is repelled by the piston during the first stage of its upward movement into the cylinder (when the intake valve is closing but is still opened).
The known device is used along an intake channel and it is not described nor is its operation along an exhaust duct suggested. It is always external to the exhaust duct and its use modifies the length of the intake system with the consequences which are explained below. This device does not create more than one (annular) duct portion within the tube where the barrel-shaped element is located. Hence, though its reduces the tube's cross-section, due to its location along the path of the gas threads towards the engine, it operates as an-obstacle to the gas flow. In fact, the barrel-shaped element slows down the quickest gas threads located along the longitudinal (central) axis of the tube by deviating them against the tube wall where, due to the friction with the tube wall, they slow down. There is no dragging effect on the slowest gas threads into the gas flow towards the engine and therefore the velocity of the flow is reduced and as a consequence the flow rate and the filling of the cylinder are reduced.
French Patent No. 818,457 describes devices which, according to the prior art, allow a better flow of the exhaust gas towards an exhaust channel. This prior art describes only this use (in an exhaust channel) but neither describes nor suggests the use of such devices in an intake duct FR 818,457 describes annular elements, freely located (excepted for the last element which is fixed) inside a channel. Each element has a jacked abutting on the channel wall and a central hole through which the exhaust gas flows.
Each of these elements restricts the channel cross-section, and also creates only one free section or portion wherein the gas flows. Therefore, during its path towards the exhaust the gas flow is slowed down by the jackets of the annular bodies which negatively affects the exhaust speed of the gas from the cylinder and therefore the engine performance.
Furthermore, the above bodies tend to cool the gas as it flows and this contributes to the slowing down the flow with obvious consequences on the emptying of spent gas from the cylinder.
British Patent No. 478,575 relates to a device to expedite and facilitate the discharge of the exhaust gases form internal combustion engines. This is obtained by arranging in the collector or chamber at or near the transition zone from the exhaust pipe or pipes to the collector or chamber, a series of aerofoils or slotted aerofoils, the arrangements being such that the gases passing over the surface of the aerofoils at high speed create a depression or vacuum within the collector or chamber which tends to draw the gases out of the exhaust pipe or pipes opening into the collector or chamber.
In this prior art reference, the aerofoils are located outside any exhaust pipe and is neither described nor suggested their location inside the pipe or within an intake duct. Furthermore, the aerofoils (which are alternate solid parts) are located within a body to which the above pipe is connected and which has a relatively large dimension. In view of this, the known solution could never be used in a modern compact engine.
German Patent Publication No. DE 37 34 616 describes the location, within a conical body connected to an exhaust duct of a combustion engine, of a tapered element (conical body) which negatively affects the gas flow. Within the conical body, the element creates only one annular section and is fixed to the wall of the conical body; it divides the single channel for the gas in a plurality of portions (creating the annular duct) which taper in the direction of the gas flow.
This known solution is not used in an exhaust duct or intake duct and has the same drawbacks as DE 1 914 859.